package org.bouncycastle.asn1.x509;

import org.bouncycastle.asn1.DERBitString;

/**
 * The KeyUsage object.
 * 
 * <pre>
 *    id-ce-keyUsage OBJECT IDENTIFIER ::=  { id-ce 15 }
 * 
 *    KeyUsage ::= BIT STRING {
 *         digitalSignature        (0),
 *         nonRepudiation          (1),
 *         keyEncipherment         (2),
 *         dataEncipherment        (3),
 *         keyAgreement            (4),
 *         keyCertSign             (5),
 *         cRLSign                 (6),
 *         encipherOnly            (7),
 *         decipherOnly            (8) }
 * </pre>
 */
public class KeyUsage extends DERBitString {
    public static final int digitalSignature = (1 << 7);
    public static final int nonRepudiation = (1 << 6);
    public static final int keyEncipherment = (1 << 5);
    public static final int dataEncipherment = (1 << 4);
    public static final int keyAgreement = (1 << 3);
    public static final int keyCertSign = (1 << 2);
    public static final int cRLSign = (1 << 1);
    public static final int encipherOnly = (1 << 0);
    public static final int decipherOnly = (1 << 15);

    public static DERBitString getInstance(Object obj) // needs to be
                                                       // DERBitString for other
                                                       // VMs
    {
        if (obj instanceof KeyUsage) {
            return (KeyUsage) obj;
        }

        if (obj instanceof X509Extension) {
            return new KeyUsage(DERBitString.getInstance(X509Extension
                    .convertValueToObject((X509Extension) obj)));
        }

        return new KeyUsage(DERBitString.getInstance(obj));
    }

    /**
     * Basic constructor.
     * 
     * @param usage
     *            - the bitwise OR of the Key Usage flags giving the allowed
     *            uses for the key. e.g. (KeyUsage.keyEncipherment |
     *            KeyUsage.dataEncipherment)
     */
    public KeyUsage(int usage) {
        super(getBytes(usage), getPadBits(usage));
    }

    public KeyUsage(DERBitString usage) {
        super(usage.getBytes(), usage.getPadBits());
    }

    public String toString() {
        if (data.length == 1) {
            return "KeyUsage: 0x" + Integer.toHexString(data[0] & 0xff);
        }
        return "KeyUsage: 0x"
                + Integer.toHexString((data[1] & 0xff) << 8 | (data[0] & 0xff));
    }
}
